Boron tribromide → 2-chloro-1H-benzo[d]imidazol-5-ol

HRID 454181Notes

Reaction equation

HRID 454181 reaction equation
[Cl:1][C:2]1[NH:3][C:4]2[CH:10]=[C:9]([O:11]C)[CH:8]=[CH:7][C:5]=2[N:6]=1.B(Br)(Br)Br>ClCCl>[Cl:1][C:2]1[NH:3][C:4]2[CH:10]=[C:9]([OH:11])[CH:8]=[CH:7][C:5]=2[N:6]=1

Participants

4

Reactant 2

HCID 25134Boron tribromideHCID 5191972-Chloro-5-methoxy-1H-benzimidazole

Product 1

HCID 220309582-chloro-1H-benzo[d]imidazol-5-olYield 159.1%

Reagents, catalysts & solvents 1

HCID 6344DichloromethaneSolvent

Procedure

2-Chloro-5-methoxybenzimidazole (0.3 g, 1.64 mmol) was suspended in dichloromethane (20 ml) under argon followed by the addition of boron tribromide (233 ul, 2.46 mmol). The reaction mixture was stirred for 2 hours at ambient temperature. The solvent was evaporated and the resulting powder was added in portions to methanol (30 ml). Silica was added and the solvent was evaporated. The resulting powder was placed on the top of a silica column and the product was eluted off using dichloromethane/methanol (95/5). Evaporation of the solvent and trituration in ether gave 2-chloro-5-hydroxybenzimidazole (440 mg, 99%).

Workup

  1. customThe solvent was evaporated
  2. additionthe resulting powder was added in portions to methanol (30 ml)
  3. additionSilica was added
  4. customthe solvent was evaporated
  5. washthe product was eluted off
  6. customEvaporation of the solvent and trituration in ether

Sources & evidence

ORD record
ord-c6a16ab737e4468b944ce467d07b7152
Source dataset
uspto-grants-2013_07
Patent number
US08492560B2

Reaction notes

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